U.S. patent application number 15/101434 was filed with the patent office on 2016-10-20 for apparatus and method for control of seismic survey equipment.
The applicant listed for this patent is WESTERNGECO L.L.C.. Invention is credited to Leendert Combee.
Application Number | 20160304172 15/101434 |
Document ID | / |
Family ID | 53274135 |
Filed Date | 2016-10-20 |
United States Patent
Application |
20160304172 |
Kind Code |
A1 |
Combee; Leendert |
October 20, 2016 |
APPARATUS AND METHOD FOR CONTROL OF SEISMIC SURVEY EQUIPMENT
Abstract
An unmanned water vessel can include a body defining an internal
volume and having a shape adapted to travel through water, with a
front and a back; at least one directional device that is exposed
to the flow of water past the vehicle when the vehicle travels in a
forward direction, the directional device having a first position
that provides an angle of attack through the water flow and a
second position that provides a second angle of attach through the
water flow; and a control system that provides commands to the at
least one directional device in view of a starting point, an end
point, and at least information about water flow expected to be
encountered by the water vessel during travel.
Inventors: |
Combee; Leendert; (Asker,
NO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WESTERNGECO L.L.C. |
Houston |
TX |
US |
|
|
Family ID: |
53274135 |
Appl. No.: |
15/101434 |
Filed: |
December 4, 2014 |
PCT Filed: |
December 4, 2014 |
PCT NO: |
PCT/US2014/068643 |
371 Date: |
June 3, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61911867 |
Dec 4, 2013 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G05D 1/0206 20130101;
G01V 1/3843 20130101; B63G 8/16 20130101; B63G 2008/005 20130101;
B63G 8/001 20130101; B63G 8/26 20130101; B63G 2008/004 20130101;
B63H 25/46 20130101; B63H 25/06 20130101; B63B 2035/007 20130101;
G01C 21/203 20130101; B63B 2035/008 20130101; B63G 8/20 20130101;
B63B 35/00 20130101; Y02T 70/00 20130101; B63B 49/00 20130101; B63G
8/18 20130101; B63H 25/42 20130101; B63G 8/42 20130101; G01V 1/3835
20130101; G01V 1/3817 20130101; B63H 25/52 20130101; Y02T 70/747
20130101; B63H 25/04 20130101 |
International
Class: |
B63B 35/00 20060101
B63B035/00; B63B 49/00 20060101 B63B049/00; G01V 1/38 20060101
G01V001/38; G05D 1/02 20060101 G05D001/02 |
Claims
1. An unmanned water vessel comprising: a body having a shape
adapted to travel through water; at least one directional device
that is exposed to the flow of water past the vessel when the
vessel travels in a forward direction, the directional device
having a first position that provides an angle of attack through
the water flow and a second position that provides a second angle
of attack through the water flow; a control system that processes
positioning information for the vessel, and provides commands to
the at least one directional device in view of a defined starting
point, end point, and at least information about water movement
expected to be encountered by the water vessel during future travel
between the starting point and the end point; and a seismic sensor
connected with the body.
2. The unmanned water vessel of claim 1, comprising at least a two
axis accelerometer, and at least one inclinometer.
3. The unmanned water vessel of claim 2, comprising a compass that
determines the heading of the vessel.
4. The unmanned water vehicle of claim 1, comprising acoustic
sensors that detect acoustic signals from at least two acoustic
sources, and wherein the control system evaluates the time
differential of arrival of the acoustic signals and calculates
position of the vehicle.
5. The unmanned water vessel of claim 1, comprising an acoustic
source that produces an acoustic signal to be detected by at least
two acoustic receives to thereby determine position of the
vessel.
6. The unmanned water vessel of claim 1, comprising a power storage
device that is connected with a motor that propels the vessel.
7. An unmanned water vessel comprising: a body having a shape
adapted to travel through water; at least one propulsion device
that has a first setting that does not provide steering force to
the vessel, and a second setting that provides a steering force to
the vessel; and a control system that provides commands to the at
least one propulsion device to select between the first and second
setting in view of an end point, and at least information about
water movement expected to be encountered by the water vessel
during travel.
8. The unmanned water vessel of claim 1, comprising at least a two
axis accelerometer, and at least one inclinometer.
9. The unmanned water vessel of claim 1, comprising a compass.
10. The unmanned water vehicle of claim 1, comprising acoustic
sensors that detect acoustic signals from at least two acoustic
sources, and wherein the control system evaluates the time
differential of arrival of the acoustic signals and calculates
position of the vehicle.
11. The unmanned water vessel of claim 1, comprising an acoustic
source that produces an acoustic signal to be detected by at least
two acoustic receives to thereby determine position of the
vessel.
12. A method of traveling an unmanned water vessel from a start
position to an end position, comprising: selecting a starting
position based at least in part of water movement information for
water that is expected to be encountered by the water vessel over
the course of future travel; and steering the unmanned water vessel
at least based on the water movement information.
13. The method of claim 12, comprising steering the unmanned water
vessel to a location on the seabed.
14. The method of claim 12, comprising adjusting a propulsion
device on the unmanned water vessel to steer.
15. The method of claim 12, comprising adjusting a propulsion
device on the unmanned water vessel to steer the unmanned water
vessel.
16. The method of claim 12, comprising moving a directional device
having a first position that provides an angle of attack through
the water and a second position that provides a different angle of
attack through the water, between the first and the second position
thereby steering the vessel.
17. The method of claim 12, comprising determining the position of
the unmanned water vessel over the course of future travel at
various points.
18. The method of claim 14, wherein the determining of the position
is done by way of measuring travel time of acoustic signals
produced by at least two acoustic signal generators with known
positions.
19. The method of claim 14, wherein the determination of the
position is done by way of measuring travel time of an acoustic
signal produced by the water vessel with at least two acoustic
receivers having known positions.
20. The unmanned water vessel of claim 1, comprising a buoyancy
control device.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/911,867 that was filed on Dec. 4, 2013, the
entirely of which is incorporated herein by reference.
TECHNICAL FIELD
[0002] The present application relates to water and/or ocean vessel
travel and navigation, and more particularly to using future
current or other exterior force information to better predict, plan
and/or implement optimal travel of the vessel.
BACKGROUND
[0003] Seismic surveying can be applied to the search and
evaluation of subterranean hydrocarbons. One type of seismic survey
is generally referred to as a towed marine survey, and includes a
manned vessel towing a series of seismic streamers (containing
seismic sensors) behind the vessel, and creating an impulse that
travels through the water and into the formation, where the impulse
reflects and reverberates back to the streamers through the water.
The signals are detected and recorded by the sensors, and data is
produced. This data can be analyzed and processed to provide
information (often images) to represent aspects of the formation
such as presence of minerals such as hydrocarbons, or lack
thereof.
[0004] Land surveys are different from marine surveys in that they
occur on "dry" land (or shallow water such as swamps or wetland).
Large numbers of sensors are placed on or in the ground, an impulse
is provided into the ground and reflects and reverberates against
the formation, and the sensors detect the signals. The detected
signals are recorded as data that can be analyzed and processed to
provide information (often images) to represent aspects of the
formation such as presence of minerals such as hydrocarbons, or
lack thereof.
[0005] Towed marine surveys are not suitable for every marine
survey situation. Thus, seabed surveys can be used. In seabed
surveys the principals of the sensors and the impulse are similar,
but sensors are placed directly on, into, or very close to the
seabed. The sensors can be in the form of nodes (similar to land)
or as cables containing sensors (similar to those used in marine
surveys), or a combination thereof.
[0006] Deployment and retrieval of the sensors for seabed surveys
in such a way as to be useful and efficient enough to allow for a
technically and commercially successful survey is difficult.
[0007] The present application provides a number of combined
features to address unmet needs in those areas.
SUMMARY
[0008] The summary presented herein is to help the understanding of
one skilled in the art with respect to the combinations of embodied
features disclosed here. They are not meant in any way to unduly
limit any present or future claims related to this application.
[0009] Various embodiments relate to a water vessel having a body
having a shape adapted to travel through water; at least one
directional device that is exposed to the movement of water past
the vehicle when the vehicle travels in a forward direction, the
directional device having a first position that provides an angle
of attack through the water flow and a second position that
provides a second angle of attach through the water flow; and a
control system that provides commands to the at least one
directional device in view of an end point, and at least
information about water movement expected to be encountered by the
water vessel during travel.
[0010] Various embodiments relate to a water vessel comprising: a
body having a shape adapted to travel through water; at least one
propulsion device that has a first setting that does not provide
steering force to the vessel, and a second setting that provides a
steering force to the vessel; a control system that provides
commands to the at least one propulsion device to select between
the first and second setting in view of an end point, and at least
information about water movement expected to be encountered by the
water vessel during travel.
[0011] Various embodiments relate to a method of traveling an
unmanned water vessel from a start position to an end position
including selecting a starting position based at least in part of
water movement information for water that is expected to be
encountered by the water vessel over the course of travel; and
steering the unmanned water vessel at least based on the water
movement information.
DESCRIPTION OF THE FIGURES
[0012] The figures presented herein are to help the understanding
of one skilled in the art with respect to the combinations of
embodied features disclosed here. They are not meant in any way to
unduly limit any present or future claims related to this
application.
[0013] FIG. 1 is a schematic of various embodied features.
[0014] FIG. 2 is a schematic of various embodied features.
[0015] FIG. 3 is a schematic of various embodied features including
cross current.
[0016] FIG. 4 is a schematic of various embodied features.
[0017] FIG. 5 is a schematic of various embodied features,
including recovery features.
[0018] FIG. 6 is a schematic of various embodied features.
[0019] FIG. 7 is a schematic of various embodied features,
including recovery features.
[0020] FIG. 8 is a schematic of various embodies features.
DETAILED DESCRIPTION
[0021] The following detailed description is presented to help one
skilled in the art understand the various combinations of embodied
features described herein, and is not meant in any way to unduly
limit any present or future claims related to this application.
[0022] This present application describes a number of combinations
of embodied features. The present application describes a method
for deploying, relocating and recovering autonomous or
semi-autonomous, or remote controlled, surface and/or underwater
unmanned marine surveying vessels, including buoys, gliders,
underwater marine gliders and autonomous underwater vessels, so as
to improve power consumption and efficiency of travel from one
point to another, in view of various external forces such as water
flow, ocean currents, wind, thermal inclines or declines, or other
external forces.
[0023] Marine surveying, including seismic surveying, may be based
on deploying autonomous or remote marine vessels in the sea (or
other body of water). Such deployment can be at the surface of the
sea. These can be unmanned vessels. Some types of vessels can
remain at the surface. Other types of vessels may descend below the
surface into the water-column, including vessels that descend to
the seabed, and including vessels that glide through the
water-column.
[0024] U.S. Pat. No. 6,951,138 provides description of one such
vessel, and is incorporated herein by reference in its entirety.
U.S. Pat. No. No. 8,717,844 describes a vessel that adjusts
buoyancy and rises and falls in the water, thereby propelling
itself forward, and is incorporated herein by reference in its
entirety. U.S. Pat. No. 7,965,583 describes another vessel and is
incorporated herein by reference in its entirety. It is noted that
many of the ideas and designs in the present application are not
vessel specific and can be applied to a number of different
variations of vessel.
[0025] Some vessels may be passive or essentially passive, i.e.,
they do not at all, minimally, or intermittently employ a powered
thruster. One type of vessel drops by its low buoyancy from an
upper level of the water toward the ocean bottom. Another use is
propellers that rotate and produce force in a direction. Another
uses a jet thruster. Vessels can similarly use high buoyancy to
travel from a lower location in the water upward, and use fins to
direct the device and control the path of travel, including lateral
movement forward or backward. Vessels can also use wind, wave
movement, and current as a primary source of propulsion. Other
embodiments of a vessel can be powered at all times, or
substantially all the time. These can use drift also, but rely on
power for final guidance and movement when near the destination
location.
[0026] As noted above, fins (or other flow deflector devices) may
be used to actively control the forces experienced by the vessel
and thus the travel direction though the water. Also the propulsion
device, such as a propeller or jet thruster, can be angled to
provide steering and guidance. For passive or essentially passive
vessels, thrusters can be used intermittently for positioning and
steering. Multiple thrusters can be positioned on the vessel to
provide force to move the vessel linearly, and/or to provide
rotational force to the vessel (singularly or multiple thrusters
used together). Fins or rudders can be used to steer the vessel.
Also, buoyancy devices can control rise and fall of a vessel in
water and be used for vertical steering.
[0027] Vessels can have active propulsion deriving power from at
least one source of non-renewable energy (electric batteries, fuel
cell, fuel, gasoline engines). Also, the vessels can have
components of renewable energy such as solar power, wave power, or
wind power. Non-renewable and renewable energy sources can both be
used on a single vessel, such as solar power to charge batteries.
In any event, it is still valuable to choose an efficient
deployment position and steer advantageously to provide efficient
travel.
[0028] Geophysical surveying--including seismic and/or
electromagnetic surveying--may simultaneously operate a large group
(10's to 100's to 1000's) of marine vehicles within one surveying
area. Because large numbers of devices may need to be stored,
deployed and recovered, their size can be limited, and hence there
can be a limited and restricted volume within each vessel for power
storage hardware. As a result, the total stored power available can
be restricted and various possibilities for limiting the overall
power consumption can be beneficial. Various combinations of
embodied features herein describe systems and methods for
optimizing the overall power consumption of said vessel for a given
travel from one point to another when faced with external forces
such as water movement.
[0029] According to embodiments, the present application describes
methods for deploying, recovering and relocating vessels that will
travel from a first location to a second location, such as being
located at a point on the surface of the sea and traveling to the
seabed, when exposed to water movement over the expected course of
travel.
[0030] In a method of geophysical surveying envisaged, 10's, 100's
to 1000's of devices may be deployed from a surface marine vessel
at the surface of the sea and by gliding and/or propelled motion,
travel to locations on the seabed. These devices may also, by
gliding and/or propelled motion, navigate towards a predefined
final position or area, on the sea-surface or on the seabed. Over
the course of travel water movement will apply various forces to
the vessel.
[0031] Devices that navigate to the seabed can remain at the seabed
for a certain period of time (minutes, hours, days, weeks) before
they either return to the surface or relocate to another seabed
position. In that situation the vessels can act as seismic nodes
while on the seabed. While on the seabed, these vessels may make
measurements of a geophysical nature, for example: seismic
measurements, electromagnetic measurements, gravity measurements,
biological measurements, chemical measurements, and so on. As a
result, a significant amount of time is spent in motion in order to
navigate to and from positions on the seabed. In order to reach
these positions within accuracy (typically between 1 meter and
several meters), external thrust may be used to navigate and steer
the devices. As a result, aside from the power used to operate the
measurement equipment (sensors, analogue amplifiers, digitization
circuits, memory and clock, processing units, telecommunication and
navigation systems including compasses, inertial sensors, gyros,
modems, antennas etc.) available battery power is used for
navigating from the deployment position to the seabed position,
from the seabed position to the recovery position, and, if
applicable, the relocation from one seabed position to a next
seabed position.
[0032] As shown in FIG. 1, the trajectory of a vessel 1 can follow
from a position A2 to a next position B1. This trajectory can be
along the surface (two dimensions), underwater (two or three
dimensions), or a combination thereof. As shown in FIG. 1, the
travel path (trajectory) 2 is a straight line.
[0033] Often times the vessel experiences external forces (such as
water movement) along its trip from point A2 to point B1. These
forces can affect the direction the vessel steers in order to
arrive at point A2, the time it takes to travel, and the velocity
of the vessel. Drift due to external sea-current may constitute an
impediment for a gliding device--be it on the surface or below the
surface in the water--to reach its desired position in a timely
manner along a predefined trajectory. A vessel's speed may be
between 0.5-1.5 knots whereas sea-currents may be up to 1 knot but
may be much larger in certain areas. As a result, the proper
trajectory and steering may be impacted by the induced drift due to
sea-currents. With a vessel traveling by way of drifting, in view
of the direction of the sea-currents the net result may be that for
a period of time the device will actually drift away from the
desired final location instead of towards it. This can be the case
with non-linear currents such as large eddies.
[0034] FIG. 2 shows an effect of a sea current 4 flowing against
the travel path 10 of the vessel 1. In FIG. 2, when the vessel
travels from point A2 to B1, along path 10, the sea current 4 works
against the vessel 1. In the case where the vessel 1 travels from
point A1 to B1 along path 11, the sea current 4 works with the
vessel.
[0035] If the sea-current data indicates that there is a
substantial sea-current in the direction as indicated by the arrow
4, then deploying a vessel at position A2 will imply that the
device will move against the current. If the current is too strong,
or a minimum traverse-speed is to be maintained etc., it could
become necessary to engage external propulsion and thus use stored
power. It can therefore be beneficial to deploy a vessel 1 at
position A1 instead such that the vessel can drift with the current
4. By taking into account the average glide speed and sea-current
strength and direction an optimal area or position of deployment
can be estimated such that there is a minimal engagement of
propulsion in order to arrive at the intended final destination B1.
This estimation can be done with a computer processor.
[0036] FIG. 3 shows effect of a cross sea current 4. In FIG. 3, as
a vessel 1 travels from point A3 to point B1 along path 12, the sea
current 4 works with the vessel 1. As a vessel 1 travels from point
A1 to B1 along path 13, the vessel 1 accounts for the cross sea
current 4 by turning left to partially go against the flow 4. If
the vessel 1 is not turned, the vessel 1 will instead travel along
path 14 due to drift.
[0037] According to the present application, there are a number of
embodied features that can address this issue. One is to use a
computer processor (which can be on the vessel) that takes into
account the sea current 4 (known or measured) when initial location
of the vessel is selected. As shown in FIG. 3, the vessel 1 could
be placed at point A3, upstream of the intended destination B1,
instead of at point A1. In that case, the vessel could drift with
the sea current 3 and arrive at point B1, without needing to steer
or alter direction.
[0038] Another is to use the computer processor to account for the
water movement 4 and initial placement at A1. In that case, If the
vessel 1 starts at A1 and travels to B1, the vessel 1 can take into
account the water flow and steer itself partially to the left
(toward A3) to counteract the water flow 4, thereby traveling along
the path 13 with global reference. Similarly, the computer
processor can select point A1' as a starting point, and the vessel
1 can aim itself perpendicular to the flow 4, thereby traveling in
a global reference along path 15 toward B1 and path 16 with
reference to the water.
[0039] Other factors that act in similar ways to sea current (water
flow), as described above, can be wind, thermal movement of water
(vertical or other directions), change in density or water, and/or
eddies created by sea current. These factors can be input to the
computer processor and vessel ahead of time, or can be detected in
real time. It should be noted that in FIG. 3 the sea current is
shown traveling linearly, but can travel along any non-linear
curved path and be similarly accounted for. A vessel entering a
curved eddy can use the computer processor to account for the
curved flow of the eddy to determine where the vessel will be
taken, and account for such accordingly.
[0040] The sea current (and other movements of water) can be
determined in a number of ways. The sea current can be known from
records, such as currents and tide charts. It can also be detected
contemporaneously. Sonar devices can be used to detect current
flow, and such can be located on an unmanned vehicle or a larger
manned vessel. The vehicle can sense its movement and thereby
deduce water movement acting upon the vessel.
[0041] The vessel can use the information relating to the currents
in order to better guide and position itself with respect to its
angle and direction of travel though the water so as to expect
reduced amounts of energy and take less time during travel. Also,
the vessel can use propulsion to compensate for forces acting upon
the vessel by water currents.
[0042] In order to overcome the effect of drift induced by
sea-currents, propulsion, for example one or more motorized
propellers powered by batteries (non-rechargeable or rechargeable)
via a control circuitry, may be used. The control circuitry
(working with the computer processor) can decide whether to
activate the propulsion system and in what manner. Motorized
propellers will draw power and may drain the battery capacity when
engaged. Therefore, it can be beneficial to reduce the need for
engaging the propulsion system. Various embodiments described here
can help reduce the need to engage the propulsion system.
[0043] As shown in FIG. 4, vessels 1 may be deployed from positions
A1, A2, or A3 (and so on). The choice of deployment position may
also take into account other vessels (not shown) to be deployed
simultaneously or sequentially with other devices. As shown in the
drawing, a vessel may be deployed from position A2. A sea current 4
acts on the vessels.
[0044] FIG. 5 shows these principals with respect to a collection
of vessels. On recovery, the same principle applies. If the vessels
are recovered along the same line as deployment, the devices may
use external propulsion, not only to navigate against the current
towards the original deployment position, but also may use
propulsion to maintain the said positions until a vessel is
available for recovery. According to various combinations of
embodied features, it can be predicted that the devices will move
in the direction as indicated by the sea-current 4 and thus may be
recovered at positions R1, R2, R3 etc. Propulsion may be needed
only at the very final stage where the devices are close to but not
exactly in the vicinity of the recovery vessel and active
propulsion is used to propel them to the final surface locations
R1, R2, R3 etc., but the overall power used can be reduced.
[0045] As shown in FIG. 6, for travel from positions B1, B2, B3 to
positions C1, C2, C3 it may be clear that if the sea-currents are
in the direction of the arrow 4, the optimal trajectories are from
B1 to C1 and from B2 to C2 and from B3 to C3 as indicated in FIG. 6
along the paths shown. Additional propulsion may be needed to
ensure that the devices will reach exactly the desired final
positions C1, C2, C3 but is not needed to compensate for any
drift.
[0046] However, in the case of a change in current direction as
indicated in FIG. 7, it may be advantageous to direct a vessel from
B1 to C2 and similarly a vessel from B2 to C3. It will thus be
helpful to deploy an extra vessel from position A4 towards final
position C1 and a recovery vehicle at a position R4. This scenario
can reduce the overall consumption of power due to the need of
propulsion that would be required if the vessel was to relocate
from B1 to C1 and so on. This is applicable when a large number of
nodes are "hopping" in unison in a coordinated grid configuration
where the direction the grid is intended to "hop" is at least
partially faced with a cross flow of water.
[0047] FIG. 8 shows a vessel traveling from point A1 to B1, where
two separate cross movements of water are expected to be
encountered. The first water movement is shown by the arrow 16 and
generally moves in a first direction. Second water movement is
shown by the arrow 17 and generally moves in a second direction
that is different and counter to the first. FIG. 8 shows the
directions being opposite to one another, but they can be in any
orientation with respect to one another, including substantially
right angles, collinear, or opposite. The vessel in FIG. 8 can take
into account the two water movements 16 and 17 when determining an
advantageous deployment location for the vessel so as to
efficiently travel to B1. The vessel 1 can also address this by
using the computer processor onboard to steer the vessel left and
right (in the figure) to account for the flows 16 and 17, thus
essentially maintaining the straight trajectory 18. An advantageous
starting point such as A1' can be set in view of the flows 16 and
17, so that the computer processor on the vessel 1 can in view of
the water movement (flow 16 and 17) keep the vessel aimed parallel
to path 18, while taking the curved trajectory 19 on a global
reference toward B1. A processor that did not take into account the
future exposure to flows 16 and 17 may be deployed at A1' and
merely aim the vessel 1 at B1 without taking into account the
future encounter with the water flows, and thus not operate
optimally.
[0048] The decision processes may be based on at least travel
(trajectory) length, travel speed, water movement, direction and
speed, and the amount of power available and required for
subsequent relocations before recovery.
[0049] When large numbers of devices are deployed--such as swarms
of 100's or 1000's devices--the trajectory information of some or
all devices may be used to alter the course of any or all devices
in real-time. For example, if the initial estimate of the current
is along a direction, the devices may be designated to relocate
from one location to another location. If however it is found that
the devices are drifting sideways due to a sideways sea-current
(which can be measured by accelerometers), then the sea-current
information may be updated leading to a change in the (optimal)
trajectory (and related steering of the vessel) and final position
information for each device so as to make the overall power
consumption of the device and/or group of devices at an acceptable
level.
[0050] Sea-current information can be collected in advance of the
deployment, recovery and/or relocation of vessels. The information
may contain data on the direction and strength of sea-currents, on
the surface and at depth. The data may also include a time
dependent component, for example representing tidal information.
The data may be obtained from historic measurements as well as
real-time or near real-time measurement in the surveying area. Real
time measurement data can be obtained via sonar based current
measurement systems. Also the trajectory data from already deployed
or recovered devices can add to the information on sea-currents at
the surveying area.
[0051] Using the sea-current information and thereby expected drift
of a deployed vessel, one may calculate the optimal deployment and
recovery locations and/or times such that the vessel may reach its
final position with a minimum use of non-renewable power for
propulsion that otherwise would be needed to correct the actual
trajectory for sea-current induced drifts. By using the available
information on sea-currents, it will be possible to deploy and
recover the vessels at locations such that reduced amount of power
is used to actively propel the vessels with respect to the
current.
[0052] In addition, when relocating vessels from a set of
stationary positions B to a second set of stationary positions
C--where B and C may be located at the sea surface or at the
seabed--it can be advantageous to incorporate the information on
the sea currents to decide which vessels from one position will
relocate to another position. In order to ensure that all positions
are occupied by a vessel, additional devices may be deployed. Those
would typically be vessels for which the relocation to the
remaining positions would consume too much power to be
efficient.
[0053] Path planning methods may be used to derive the likely path
and the uncertainty therein. Using said methods can be used
recursively to determine the optimal positions as described in the
present application. These calculations can be done by a computer
processor on board the unmanned vessels.
[0054] There are a number of ways that the vessels can determine
position during travel. One way is by GPS (Global Positioning
Systems), which may best be used on the surface of water or when in
communication with satellites. GPS uses signals from satellites to
triangulate position. Similar principals can be used with land
based signal sources (as opposed to satellites).
[0055] Acoustic sources from known locations can be used to
determine position of the vessel. In that case, the acoustic signal
can be sent at a known time, and based on the time travel the
position of the vessel can be determined. Similarly, the vessel can
produce an acoustic signal and based on the arrival of that signal
at two or more receivers with known locations, the vessel position
can be determined. Acoustic sources and/or receivers used to
determine positon of a vessel can be located on or near the seabed,
on vessels, on buoys, or on other vessels, so long as the position
of the acoustic sources and/or receivers is known.
[0056] Pressure sensors can determine depth of the vessel, and can
be used in connection with acoustic ranging devices to triangulate
the position of the vessel.
[0057] An accelerometer and inclinometer or gyroscope can also be
used to determine the travel and angular position of the vessel
with respect to a known start position. A compass can be
incorporated into and can be used to determine the heading of a
vessel. By measuring acceleration and knowing how the vessel is
positioned angularly, the position of the vessel can be estimated
with respect to a start position. If a vessel starts at a position,
and it is determined to accelerate along an x axis for a determined
time, the resulting velocity and distance traveled can be derived.
Similarly, the trajectory travel path can be determined to provide
the vessel position with respect to the start position and end
position. This can be done for two and three axes, so that the path
of travel can be determined.
[0058] With a determined position during travel, known water
movement and updated water movement information can be used by, as
noted, the computer processor to steer and direct the vessel to
advantageously travel to an end position.
[0059] A seismic sensor can be connected with the body of the
vessel. The seismic sensor can be a hydrophone or a geophone or an
accelerometer, and combinations therefor. They can be connected
with a cable that connects with the vessel, or incorporated more
closely with the vessel and into the vessel body.
[0060] For seabed applications, seismic sensors can be adapted to
be coupled to the seabed when the vessel sits on the seabed.
Coupling can be established by pressure applied by the body of the
vessel pressing the sensor to the seabed. Coupling can be
established by digging with water moved by the propulsion device,
or other digging devices connected with the vehicle. Coupling can
be established by way of the shape of the sensors or housings of
the sensors having angled or pointed projections that penetrate
into the top surface of the seabed. Coupling can be established by
way of the shape of the vessel housing the seismic sensor. The
vessel can have a pointed shape that when dropped onto the seabed
tends to drive into or penetrate the stop surface of the seabed
thereby aiding establishment of the coupling.
[0061] The preceding description is mean to aid the understanding
of one skilled in the art, and is not meant in any way to unduly
limit the scope of any present or future claims relating to this
application.
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